Such a mechanism for attaching the rotating plate as described above is disclosed, for example, in Japanese Utility Model Registration Publication No. 57-13302.
The mechanism for attaching the rotating plate to the head protector in the helmet, disclosed in Japanese Utility Model Registration Publication No. 57-13302 (hereinafter described as "the conventional mechanism for attaching the shield plate") has a narrow base plate attached to the front side of the head protector of the helmet. Rotatably attached to this base plate are the right and left sides of a shield plate with a pair of right and left attaching shafts, respectively. Further, an intermediate plate lies between the base plate and the shield plate, and a protrusion projecting from the outer side surface of the intermediate plate and serving as a stopper is fitted into an opening of the shield plate, so that the intermediate plate is rotatable together with the shield plate.
Moreover, in the conventional mechanism for attaching the shield plate, a circular-arcuate guide groove whose center coincides with that of the attaching shaft is disposed in the base plate, and fitted into this guide groove is a resilient cylinder, projecting from and formed integral with the inner side of the intermediate plate. The circular-arcuate guide groove is shaped from a plurality of circular openings which are shifted a little in turn and partially overlapped, so that a narrow part is formed between the adjacent openings.
In the conventional mechanism for attaching the shield plate constituted as described above, when the shield plate is moved to open or close the head protector, the resilient cylinder is moved along the circular-arcuate guide groove and fitted into one of the plurality of circular openings, so that it is possible to set the shield plate in its predetermined position that shows a one-to-one correspondence with each of the plurality of circular openings (that is, fully closed position, one-sixth opened position, one-third opened position, half-opened position, two-thirds-opened position, five-sixths opened position, or fully opened position).
However, in the conventional mechanism for attaching the shield plate, the shield plate can be merely set in its predetermined position that corresponds with one of the plurality of circular openings of the circular-arcuated guide groove, so that the shield plate can not be set in an arbitrarily opened position with respect to the head protector of the helmet. Further, when the shield plate is largely moved to open or close with respect to the head protector of the helmet, it is required to move the resilient cylinder wobblingly along the plurality of circular openings and the plurality of narrow parts, so that well clicking responses are not brought when the shield plate is thus moved.